The present invention relates to the adjustment of chairs such as swivel type chairs and more particularly to adjustments made by individual users to set the relative positioning between a chair back rest and a chair seat element to the individual comfort of the user.
In a known type of office swivel chair, a base member is connected at a rear end thereof to a pedestal, the base having a forward part that includes a tip end to which a seat plate carrier is pivoted at a forward end of the latter. A back rest carrier can be either fixed rigidly or pivotally to the rear end of a seat plate carrier, and a spring can be interposed between the seat plate carrier and the base member to push the two apart. Means such as gas springs, clamping screws or a combination of a clamping means with lamination plates are used to lock the seat plate carrier and the back rest carrier relative to the base member.
In this type of chair, a user releases the locking means and moves the back rest and seat element (mounted on the seat plate carrier) in relation to each other by shifting the user's body weight as imposed on the seat element to effect what the user judges the most comfortable positioning of these components. However, body weight of users varies considerably and since this enters into the adjustment actually made since it is involved in how the seat plate carrier will slant or be angulated on the base member, the user following setting of the back rest/seat plate carrier relation by operating the locking means, may find that the slant of these to the base member does not provide the comfort sought.
To overcome this, an arrangement (disclosed in German published application DE 3500932) was proposed by which the force necessary for making slant adjustment could be adjusted according to the user's body weight. For the type chair described above, solution was offered in which a weight adjustment means comprised of an adjustable spring element be used. For this purpose, a spring was arranged with one end connected to a bar hanging from a pivot by which a base member was connected with a seat plate carrier, the other end of the spring being attached to the base member. The spring was activated by a knob running in a thread cut into the forward part of the bar. This arrangement was found not to be satisfactory because the adjustment range was very narrow and its effect when the user made back rest/seat element adjustment not readily discernible.